The warehousing of goods in the course of their movement within commerce is a procedure essentially as old as commerce itself. Dedicated warehouse facilities function within the goods distribution process and have varied widely in scope and complexity. Generally, as working space has become scarce, storage has become vertical, resort being made to a wide range of racks and shelves seeking to maximize the utilization of valuable floor space by resort to vertical space. As vertical storage has reached practical limits, as may be dictated by the effective reach of vehicles such as forklift trucks and the like, more warehouse space has been constructed with more floor space to meet expanding need.
Particularly where larger or heavier and more bulksome items have been stored, a palleting approach has been employed for goods movement and storage. With this approach, storage racks are provided with multiple levels of bays developed with an architecture of horizontal row supports and connected columnar uprights. An early rack storage system sometimes has been referred to as "drive in pallet racking", an approach wherein the stored containers or goods are palletized or mounted upon "skids" and lowered upon small, upright mounted mutually inwardly extending mounts or brackets by a forklift type warehousing vehicle. Such warehousing inefficiently consumes floor space. For example, each bay of the racks of such an arrangement is limited to one container or single load of goods and a floor space consuming aisle is required before each array of bays. Some floor space may be saved by situating the racks in a back-to-back formation, but, as warehousing demands and costs have increased, the above approach has commenced to fall from industry favor. However, this technology of utilizing vertical working space as developed in conjunction with drive in pallet racking has importantly contributed to the efficiency of warehousing.
To achieve a higher level of efficiency of floor space utilization, a variety of storage rack structures have been developed having extended depths so that containers can be stored at more than one location within each bay of the rack structure. To access the expanded depths of the bay, trolley-like structures have been developed which are biased towards the face or accessing end of the bay either by gravitation through the use of sloping tracks or the like, or by motorized or resilient biasing systems. In general, when a first load is positioned within such bay, it is placed upon a trolley and remains at the access opening of the bay until a second load is inserted. That second load then pushes the first trolley mounted loading rearwardly. During an unloading or picking procedure, the opposite activity ensues to provide for a last in, first out (LIFO) accessing procedure. Typically for this picking procedure, the trolley mounted packages are induced to move to the pick position by the noted gravitational arrangement.
To further expand the depthwise capacity of the bays, a variety of "forward flow" developments looking to the use of multiple trolleys or the like riding within a bay have been witnessed. The implementation of such multiple trolley systems requires, however, that each load containing trolley or movable support be successively movable to the front access face or picking position of the bay for loading and pick-up procedures. Thus, trolley nesting has been employed wherein each trolley platform has a unique widthwise or horizontal extent such that a next inwardly disposed device nests over the next forwardly disposed device and all, when the bin is empty, are located at the accessing front of the bay. In effect, when the bays are empty, a vertical stack of the movable load carrying devices is presented. However, for each succeeding load supporting stage of such system, horizontal space is expended and, thus, valuable warehouse floor space is lost. For a typically large warehouse facility, that loss will become substantial. Another limitation accrues with the use of the currently evolved forward flow systems in that they are limited by the number of trolleys or carriers which can be practically nested forwardly. In general, about three to six such carrying components remain the limit of depth based capacity, depending upon the particular design involved. Another drawback to the currently developed nesting forward flow systems resides in a lack of uniformity in the sizes of each trolley employed in a multiple storage station system, as well as in the need for elaborate rail arrays and the like to accommodate for the trolleys of varying sizes. The devices also are limited in the locations in which they can be installed. Generally, it is desirable that all vertical space within a warehousing facility be used. This involves storage over access doors and the like which heretofore has been somewhat limited, principally due to the noted depth and width limitations of current forward flow systems.
Many existing warehouse facilities have been constructed having the noted early developed drive-in pallet racking systems which are structured to retain palletized goods using pallets of preset widthwise dimensions. To upgrade these structures to a more efficient LIFO gravitational forward flow approach, the pre-established pallet and bay widths have heretofore severely limited bay depth, for example to one trolley. As a consequence, the upgrading of older warehousing racking to utilize more efficient storage techniques generally has been precluded. To achieve an efficient retrofitting of these older facilities to provide extended bay depth with an expanded number of storage stations gained from forward flow based carrier systems, the width of the carrier transport systems within each bay for each station must be maintained essentially constant even though all such carrier devices must be stackable at the access opening of each bay for forklift truck provided loading and picking operations.
Of course, it is particularly desirable that any retrofit system or, in fact, any newly employed forward flow multiple station storage system be fabricable with uniform, commonly dimensioned components to achieve concomitant savings in fabrication costs, as well as in developing a modularity facilitating their ease of installation gained through a commonality of parts.